Three behavioral phenotypes are to be studied using a genetic-epidemiologic approach. 1) Phenotypic variations of specific reading disability will be characterized in subjects attending schools for learning disabled children, their sibs, parents and collateral relatives, and the hypothesis of phenotypic and genetic heterogeneity will be tested. The impact of reading disability on development and occupational choice will also be studied. 2) The hypothesis of genetic heterogeneity in schizophrenia will be tested by contrasting the phenotypic properties of patients with preadolescent and early adult onset with those of later onset. 3) The psychiatric symptoms in patients with Huntington's disease and their "at risk" children will be characterized.